The invention pertains to methods of making magnetoresistive memory devices, such as, for example, magnetic random access memory (MRAM) devices.
Numerous types of digital memories are utilized in computer system components, digital processing systems, and other applications for storing and retrieving data. MRAM is a type of digital memory in which digital bits of information comprise alternative states of magnetization of magnetic materials in memory cells. The magnetic materials can be thin ferromagnetic films. Information can be stored and retrieved from the memory devices by inductive sensing to determine a magnetization state of the devices, or by magnetoresistive sensing of the magnetization states of the memory devices. It is noted that the term xe2x80x9cmagnetoresistive devicexe2x80x9d characterizes the device and not the access method, and accordingly a magnetoresistive device can be accessed by, for example, either inductive sensing or magnetoresistive sensing methodologies.
A significant amount of research is currently being invested in magnetic digital memories, such as, for example, MRAM""s, because such memories are seen to have significant potential advantages relative to the dynamic random access memory (DRAM) components and static random access memory (SRAM) components that are presently in widespread use. For instance, a problem with DRAM is that it relies on power storage within capacitors. Such capacitors leak energy, and must be refreshed at approximately 15 nanosecond intervals. The constant refreshing of DRAM devices can drain energy from batteries utilized to power the devices, and can lead to problems with lost data since information stored in the DRAM devices is lost when power to the devices is shut down.
SRAM devices can avoid some of the problems associated with DRAM devices, in that SRAM devices do not require constant refreshing. Further, SRAM devices are typically faster than DRAM devices. However, SRAM devices take up more semiconductor real estate than do DRAM devices. As continuing efforts are made to increase the density of memory devices, semiconductor real estate becomes increasingly valuable. Accordingly, SRAM technologies are difficult to incorporate as standard memory devices in memory arrays.
MRAM devices have the potential to alleviate the problems associated with DRAM devices and SRAM devices. Specifically, MRAM devices do not require constant refreshing, but instead store data in stable magnetic states. Further, the data stored in MRAM devices can potentially remain within the devices even if power to the devices is shutdown or lost. Additionally, MRAM devices can potentially be formed to utilize less than or equal to the amount of semiconductor real estate associated with DRAM devices, and can accordingly potentially be more economical to incorporate into large memory arrays than are SRAM devices.
Although MRAM devices have potential to be utilized as digital memory devices, they are currently not widely utilized. Several problems associated with MRAM technologies remain to be addressed. It would be desirable to develop improved methodologies for making MRAM devices.
In one aspect, the invention encompasses a method of forming a magnetoresistive device. A stack is formed, with the stack comprising a first magnetic layer, a second magnetic layer, and a non-magnetic layer between the first and second magnetic layers. At least one of the first magnetic layer, second magnetic layer, and non-magnetic layer is etched with a primarily physical etch process in a reaction chamber to expose a portion of the etched layer. While the stack remains in the reaction chamber, a protective material is deposited over the exposed portion.
In another aspect, the invention encompasses another method of forming a magnetoresistive device. A stack is provided. The stack comprises a first magnetic layer, a non-magnetic layer over the first magnetic layer, and a second magnetic layer over the non-magnetic layer. The second magnetic layer is etched with a primarily physical etch process in a reaction chamber to pattern the second magnetic layer into a block having at least one exposed sidewall. While the stack remains in the reaction chamber, a protective material is deposited over the at least one exposed sidewall.